Kv channel subunits that contribute to voltage-gated K⁺ current in renal vascular smooth muscle

The rat renal arterial vasculature displays differences in K⁺ channel current phenotypes along its length. Small arcuate to cortical radial arteries express a delayed rectifier phenotype, while the predominant Kv current in larger arcuate and interlobar arteries is composed of both transient and sustained components. We sought to determine whether Kvα subunits in the rat renal interlobar and arcuate arteries form heterotetramers, which may account for the unique currents, and whether modulatory Kvβ subunits are present in renal vascular smooth muscle cells. RT-PCR indicated the presence of several different Kvα subunit isoform transcripts. Coimmunoprecipitation with immunoblotting and immunohistochemical evidence suggests that a portion of the K⁺ current phenotype is a heteromultimer containing delayed-rectifier Kv1.2 and A-type Kv1.4 channel subunits. RT-PCR and immunoblot analyses also demonstrated the presence of both Kvβ1.2 and Kvβ1.3 in renal arteries. These results suggest that heteromultimeric formation of Kvα subunits and the presence of modulatory Kvβ subunits are important factors in mediating Kv currents in the renal microvasculature and suggest a potentially critical role for these channel subunits in blood pressure regulation.